There are a number of situations wherein it is desirable to obtain video images of target subjects (e.g., persons, vehicles). Such situations include, for example, law enforcement contact with suspects, airport security checkpoints, building and public event access, and the like. Often times, however, video images obtained using visible light may not reveal prohibited materials carried by the subject or may be insufficient for further analysis. One example, is in the area of facial biometrics wherein the presence of glasses, particularly sunglasses, on a person's face can obscure the visibility of facial features such as their eyes that are important to accurate identification.
Since target subjects typically convey (i.e., reflect or emanate) optical energy therefrom other than visible light, it is possible to obtain images of target subjects based on non-visible light optical energy. One example of non-visible optical energy suitable for use in imaging subjects is IR optical energy. However, the ability to obtain high quality IR images of a subject can be effected by changing environmental conditions (e.g., ambient visible and infrared light levels). Further, different portions of the IR spectrum may be more suitable for observing different subjects and different amounts of visible and non-visible light may need to be excluded in order to obtain the optimal subject image.